JP2002080874A - Lubricant composition, magnetic recording medium and method of manufacturing magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lubricant composition which exhibits an excellent lubricating performance, and a magnetic recording medium which is improved in service reliability in e.g. travelling durability and weatherproof shelf stability without deteriorating the electromagnetic transduction characteristics. SOLUTION: The lubricant composition contains at least one compound selected from fluorinated monocarboxylic acids having a perfluoroalkyl or perfluoropolyether group and an alkyl or alkenyl group in the molecule, and at least one compound selected from fluorinated carboxylic acid esters having a fluorocarbon or perfluorocarbon group in the molecule. The lubricant composition is contained in the lubricant layer (4) of a magnetic recording medium (10) made by forming a ferromagnetic metal thin film (2), a carbonaceous material film (3) and a lubricant layer (4) in this order on one side of a nonmagnetic base plate (1), and forming a back coating layer (5) on the other side thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a lubricant composition exhibiting excellent lubricating performance, and a magnetic recording layer suitable for, for example, a digital video tape recorder, a high definition video tape recorder, and a data storage device of a computer. A magnetic recording medium having a ferromagnetic metal thin film, a carbon film thereon, and a lubricant layer thereon, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in the field of magnetic recording, high-density magnetic recording media suitable for such digital recording and reproducing apparatuses have been developed with high performance such as digitization, miniaturization, and long use time. It has been actively carried out and has recently become an extremely advantageous alternative to coating type magnetic recording media for short wavelength recording.
Metal thin film magnetic recording media have been put to practical use. In general,
The metal thin-film type magnetic recording medium refers to a tape, a disk or the like in which a magnetic layer made of a ferromagnetic metal thin film is provided as a recording layer on one surface of a nonmagnetic substrate.

However, the magnetic layer of a metal thin film type magnetic recording medium has extremely good surface properties, that is, the surface roughness of the magnetic layer is small, so that the contact area with the magnetic head increases. During the reproduction process, the magnetic head is easily worn due to a large frictional force while sliding at a high speed with the magnetic head. Abrasion of the magnetic layer has a great effect on running durability or still durability of the magnetic recording medium, and reducing it has been a major issue in research and development of metal thin-film magnetic recording media.

[0004] Therefore, attempts have been made to reduce wear by providing a lubricant layer on the surface of the magnetic layer to improve running durability and still durability. When a lubricant layer is provided, the lubricant layer on the surface of the magnetic layer has a lubricating property with a thickness of only a few nm in order to minimize output loss due to spacing loss between the magnetic recording medium and the magnetic head and to achieve high output. It is required to demonstrate. Therefore, the use of fluorine-based compounds exhibiting excellent lubrication properties has been widely studied, and the use of various compounds has been proposed. As such a compound, for example, the chemical formula (x1):

[0005]

Embedded image Fluorinated long-chain carboxylic acid ester represented by
−46431)

Chemical formula (x2):

Embedded image It has been proposed to use a fluorine-containing carboxylic acid monoester having a carboxyl group (see JP-A-61-107529).

[0007]

However, there is a severe demand for improving the performance of a magnetic recording medium, and it is difficult to obtain sufficient lubricating characteristics with the above-mentioned conventional lubricant.
Further improvements in running durability and weather storage stability are desired. The storability is determined by the degree of deterioration of various performances such as running durability after being left for a long time, and when "weather resistance" storability is good, it can be determined in any environment including severe conditions such as high temperature and high humidity. It means that a decrease in running durability or the like is small even after being left for a long time under the conditions.

In view of the above problems, the present invention provides a lubricant composition which is capable of obtaining a magnetic recording medium which is excellent in running durability and weather resistance and has high practical reliability without impairing the electromagnetic conversion characteristics. It is another object of the present invention to provide a magnetic recording medium having a lubricant layer containing the lubricant composition and a method for producing the same.

[0009]

In order to solve the above-mentioned problems, the present invention provides a compound represented by the following general formula (a) having a perfluoroalkyl group or a perfluoropolyether group and an alkyl group or an alkenyl group in the molecule. ) And at least one compound selected from the compounds represented by (b); and II) a lubricant composition comprising at least one compound selected from the compounds represented by the general formula (c):

[0010]

Embedded image (Wherein, R ¹ represents an alkyl group or an alkenyl group;
R ² represents a perfluoroalkyl group or a perfluoropolyether group; a is an integer of 0 to 20;
Or 1)

Embedded image (Wherein, R ³ represents an alkyl group or an alkenyl group;
R ⁴ represents a perfluoroalkyl group or a perfluoropolyether group, R ⁵ represents —O— or —S—,
c is an integer of 0 to 20; d is 0 or 1)

Embedded image (Wherein, R ⁶ represents a fluorine-containing organic group, R ⁷ represents an alkyl group or an alkenyl group, and n is an integer of 0 to 12).

The lubricant composition of the present invention comprises two or more specific fluorine-containing compounds, and has a general formula (a) to (c).
Are all fluorine-containing compounds. This lubricant composition comprises: I) at least one compound selected from fluorinated monocarboxylic acids represented by the general formulas (a) and (b);
And II) at least one compound selected from the fluorine-containing carboxylic acid esters represented by the general formula (c). The compound represented by formula (a) can also be said to be a fluorinated carboxylic acid monoester having one carboxyl group.

This lubricant composition is, for example, a magnetic recording medium comprising a ferromagnetic metal thin film, a carbon film and a lubricant layer formed in this order on one surface of a non-magnetic substrate (this is simply referred to as a metal thin film type magnetic recording medium). (May be referred to as a recording medium), the adhesion strength to the carbon film located below the lubricant layer is improved, and excellent lubricating properties are imparted to the magnetic recording medium. . Due to these synergistic effects, the magnetic recording medium has improved running durability and weather-preservability without impairing the electromagnetic conversion characteristics, and has extremely low scattering of the lubricant during use. can get.

According to another aspect of the present invention, a ferromagnetic metal thin film is provided on one surface of a nonmagnetic substrate, and a lubricant layer is provided on the ferromagnetic metal thin film via a carbon film. A magnetic recording medium comprising: a lubricant layer containing the lubricant composition of the present invention. By using a lubricant composition combining two or more of the above specific fluorine-containing compounds,
The adhesive strength to the carbon film located below the lubricant layer is improved, and excellent lubrication properties are imparted to the magnetic recording medium.
Due to these synergistic effects, the magnetic recording medium has improved running durability and weather-preservability without impairing the electromagnetic conversion characteristics, and has extremely low scattering of the lubricant during use. can get.

[0014] In a preferred embodiment of the magnetic recording medium of the present invention, the carbon film has a nitrogen-containing plasma polymerized film in the surface layer portion, and the lubricant layer is formed on the nitrogen-containing plasma polymerized film of the carbon film. Amino groups are present in the surface layer of the carbon film due to the nitrogen-containing plasma polymerization, and as a result, the adhesion strength between the lubricant layer and the carbon film is increased, and the durability of the magnetic recording medium is further improved. Becomes And, combined with the inclusion of a specific fluorine-containing compound or the like in the lubricant layer, the running durability and the weather storage stability have been improved with excellent lubrication characteristics without impairing the electromagnetic conversion characteristics. A high magnetic recording medium can be obtained.

Further, the present invention provides a method for producing the magnetic recording medium of the present invention. The method for manufacturing a magnetic recording medium according to the present invention is characterized in the step of forming a lubricant layer. Other manufacturing steps may be steps conventionally used for manufacturing a magnetic recording medium. The step of forming a lubricant layer in the production method of the present invention comprises applying a coating solution prepared by dissolving the above-described lubricant composition in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent, at a relative humidity of 10 to 40. % In an environment within the range of%, and a step of drying the mixed organic solvent.

By applying a coating liquid containing a lubricant composition under a specific humidity condition using a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent, the adhesion strength between the lubricant layer and the carbon film is increased. And a uniform thin lubricant layer with very little coating unevenness can be formed. Therefore, according to the manufacturing method of the present invention, it is possible to obtain a highly practical magnetic recording medium having excellent lubrication performance.

In the production method of the present invention, the mixing ratio of the hydrocarbon solvent and the alcohol solvent is 1: 1:
It is preferably in the range of 9 to 9: 1. Mixing both in this range makes it possible to minimize coating unevenness and is advantageous in terms of cost.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The fluorine-containing compound contained in the lubricant composition of the present invention is a compound represented by any one of the general formulas (a) to (c). General formula (a):

Embedded image Can be said to be a fluorine-containing carboxylic acid monoester having one carboxyl group. This compound is obtained, for example, by converting one of the two carboxyl groups contained in a dicarboxylic acid such as succinic acid into an ester.

In the general formula (a), R ¹ is an alkyl group or an alkenyl group, and R ² is a perfluoroalkyl group or a perfluoropolyether group. a is usually an integer of 0 to 20, preferably 1 to 10. b is 0 or 1.

The carbon number of R ¹ in the general formula (a) is 6 to
It is preferably 30 and more preferably 10 to 24. When the number of carbon atoms is less than 6 or more than 30, the lubricity of the lubricant composition may decrease. R ¹ may be linear or branched.

When R ² is a perfluoroalkyl group, it preferably has 6 to 12 carbon atoms,
More preferably, it is 10. R ² may be linear or branched. When R ² is a perfluoropolyether group, its molecular weight is about 20
It is preferably about 0 to about 6000, and about 300 to
More preferably, it is about 4000. Molecular weight 200
If it is less than 6000 or more than 6000, the lubricity and storage reliability of the lubricant composition may decrease.

When R ² is a perfluoropolyether group, the perfluoropolyether group is preferably one represented by any of the following formulas (d), (e) and (f). . When the compound having the following perfluoropolyether group is contained in the lubricant composition, for example, when the composition is contained in the lubricant layer of the metal thin-film magnetic recording medium, the carbon film of the lubricant layer The adhesion strength to the magnetic recording medium is further improved, and more excellent lubricating properties are imparted to the magnetic recording medium. And due to these synergistic effects,
It is possible to obtain a magnetic recording medium having improved running durability and weather storage stability without impairing the electromagnetic conversion characteristics, and having very little scattering of the lubricant during use, and having high practical reliability.

Formula (d):

Embedded image In the above, q is an integer of 1 or more.

General formula (e):

Embedded image In the formula, r and t are integers of 1 or more.

General formula (f):

Embedded imageIn, R⁸Represents a perfluoroalkyl group, and u represents
V is an integer of 1 to 30; v
Is more preferably 1 to 8. R⁸Has 1 carbon atom
Is preferably from 30 to 30, more preferably from 1 to 8.
preferable. Also, R ⁸Is branched even if it is linear
May be done.

When q, r, t, u and v in the general formulas (d), (e) and (f) are out of the above ranges,
For example, when a lubricant composition containing such a compound having a perfluoropolyether group is included in a lubricant layer of a magnetic recording medium, the lubricity and storage reliability of the magnetic recording medium may be reduced. Also, the carbon number of q, r, t, u and v and R ⁸ is such that the molecular weight of the perfluoropolyether group is in the above-mentioned preferred range, that is, about 20.
About 0 to about 6000, more preferably about 300 to about 40
It is preferable to select appropriately so as to be within the range of 00.

General formula (b):

Embedded image In the compound represented by, R ³ is an alkyl group or an alkenyl group, and R ⁴ is a perfluoroalkyl group or a perfluoropolyether group. R ⁵ is an oxygen atom or a sulfur atom. c is usually an integer of 0 to 20, preferably 1 to 10. d is 0 or 1
It is.

The carbon number of R ³ in the general formula (b) is 6 to
It is preferably 30 and more preferably 10 to 24. When the number of carbon atoms is less than 6 or more than 30, the lubricity of the lubricant composition may decrease. R ³ may be linear or branched.

When R ⁴ is a perfluoroalkyl group, it preferably has 1 to 12 carbon atoms,
More preferably, it is 10. R ⁴ may be linear or branched. When R ⁴ is a perfluoropolyether group, its molecular weight is about 20
It is preferably about 0 to about 6000, and about 300 to
More preferably, it is about 4000. Molecular weight 200
If it is less than 6000 or more than 6000, the lubricity and storage reliability of the lubricant composition may decrease.

When R ⁴ is a perfluoropolyether group, R ⁴ is represented by any of the above formulas (d), (e) and (f), similarly to R ² in formula (a). Preferably, the group is The general formulas (d), (e) and (f) are as described above in relation to the general formula (a), and the detailed description is omitted here by citing the description.

Next, the fluorine-containing carboxylic acid ester represented by the general formula (c) will be described. General formula (c):

Embedded image In the formula, R ⁶ represents a fluorine-containing organic group, R ⁷ represents an alkyl group or an alkenyl group, and n is an integer of 0 to 12.

The term "fluorine-containing organic group" as used herein refers to an organic group in which one or more hydrogen atoms have been replaced with fluorine atoms. R ⁶ is preferably a fluoroalkyl group, a fluoroalkenyl group, a fluoroether group, or a fluoropolyether group, and more preferably a perfluoroalkyl group, a perfluoroalkenyl group, a perfluoroether group, or a perfluoropoly group. It is an ether group. R ⁶ preferably has 4 to 14 carbon atoms, and 6
It is more preferable that the number is from 12 to 12. R ⁶ may be linear or branched.

In the general formula (c), n is more preferably 1 to 6. R ⁷ preferably has 8 to 22 carbon atoms, and more preferably 12 to 18 carbon atoms. R
⁷ may be linear or branched.

The lubricant composition of the present invention comprises Group I, ie,
At least one compound selected from the compounds represented by general formulas (a) and (b); and Group II,
At least one compound selected from the compounds represented by the general formula (c) is mixed. The mixing ratio of both is 1: 9 to 8: 2 (molar ratio: Group I: II
Group), more preferably 1: 9 to 5: 5.

If the proportion of the compound selected from each group in the lubricant composition is small, the following problems may occur when a lubricant layer of a magnetic recording medium is formed with the lubricant composition of the present invention. . If the proportion occupied by the compound selected from Group I is small, the lubrication performance may be reduced. II
If the proportion of the compound selected from the group is small, the lubricating performance may decrease, and the adhesion strength of the lubricant layer of the magnetic recording medium to the carbon film may decrease.

The lubricant composition of the present invention has the general formula (a)
Components other than the compound represented by (c), for example, a rust inhibitor,
Alternatively, it may contain a conventionally known lubricant. In that case, the proportion occupied by components other than the compounds represented by the general formulas (a) to (c) is preferably less than 20% by weight, more preferably less than 10% by weight, based on the total amount of the composition. .
If the content is 20% by weight or more, for example, when a lubricant layer of a magnetic recording medium is formed with this lubricant composition, good lubricating properties may not be imparted to the magnetic recording medium.

A magnetic recording medium according to a second aspect of the present invention is a magnetic recording medium in which a ferromagnetic metal thin film, a carbon film, and a lubricant layer are formed in this order on one surface of a nonmagnetic substrate. The lubricant layer contains the lubricant composition of the present invention. Then, each layer constituting the magnetic recording medium of the present invention will be described together with its manufacturing method with reference to the drawings.

FIG. 1 is a sectional view of a metal thin film type magnetic tape (hereinafter, simply referred to as a magnetic tape) which is one embodiment of the magnetic recording medium of the present invention. In this magnetic tape (10), a ferromagnetic metal thin film (2) as a magnetic layer, a carbon film (3) and a lubricant layer (4) are formed in this order on one surface of a nonmagnetic substrate (1). The back coat layer (5) was formed on the surface of the. Therefore, the structure is such that a back coat layer (5), a non-magnetic substrate (1), a ferromagnetic metal thin film (2), a carbon film (3) and a lubricant layer (4) are laminated in this order from the bottom. ing.

The layers other than the lubricant layer and the method of forming the layers are known, and conventional materials and forming methods can be employed.

For example, as the non-magnetic substrate (1), a film made of polyethylene terephthalate, polyethylene naphthalate, aromatic polyamide or aromatic polyimide, an aluminum substrate or a glass substrate can be used. In order to achieve both practical reliability and good RF output, the surface of the nonmagnetic substrate (1), that is, the surface in contact with the ferromagnetic metal thin film, has a diameter of 50 to 700 nm and a height of 5 to 70 nm.
It is preferable that a projection formation process of nm is performed. The projections are formed, for example, by dispersing and fixing ultrafine particles made of an inorganic substance such as SiO ₂ or ZnO, or ultrafine particles made of an organic substance such as imide on the surface of the nonmagnetic substrate, or It is formed by molding a polymer material containing such fine particles into a film.

The magnetic layer (2) is preferably a ferromagnetic metal thin film. The ferromagnetic metal thin film can be formed by conventional materials and methods.

Ferromagnetic metals suitable for the magnetic layer include Fe
Base metals, Co base metals, and Ni base metals. In the present invention, the ferromagnetic metal constituting the magnetic layer is particularly preferably a Co-based metal. Here, “Co-based metal” means
Cobalt and preferably 5 as a main component of cobalt
An alloy containing 0 atomic% or more. The same applies to “Fe-based metal” and “Ni-based metal”.

The ferromagnetic metal thin film is, specifically, Fe, C
o and Ni, and Co-Ni, Co-Fe, Co
-Cr, Co-Cu, Co-Pt, Co-Pd, Co-
Sn, Co-Au, Fe-Cr, Fe-Co-Ni, F
e-Cu, Ni-Cr, Fe-Co-Cr, Co-Ni
-Cr, Co-Pt-Cr and Fe-Co-Ni-C
It is formed of one or more materials selected from alloys such as r. The ferromagnetic metal film may include oxygen, which may be included in the form of oxides of these metals or alloys. The ferromagnetic metal thin film may be in the form of a single-layer film or in the form of a multilayer film.

The ferromagnetic metal thin film can be formed by an ion plating method, a sputtering method, an electron beam evaporation method, or the like. When the ferromagnetic metal thin film is formed in an oxygen atmosphere, the ferromagnetic metal thin film contains oxygen, for example, in the form of a ferromagnetic metal oxide. The thickness of the ferromagnetic metal thin film is generally 50 nm to 300 nm.

The carbon film (3) has a Vickers hardness of about 2.
It is as high as 45 × 10 ⁴ N / mm ² (about 2500 kgf / mm ² ), and as a protective layer, prevents damage to the magnetic tape together with the lubricant layer (4). In consideration of the balance between practical reliability and output, the thickness is preferably 10 nm to 20 nm. This carbon film (3) can also be formed using known materials and methods, for example, by a plasma CVD method using only a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas. Is done.

Specifically, a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas such as argon is introduced into a vacuum container, and the pressure in the container is set to 1.33 × 10 ⁻¹ to 1.33.
A discharge is generated inside the vacuum vessel while maintaining the pressure at × 10 ² Pa (0.001 to 1 Torr), a plasma of hydrocarbon gas is generated, and the carbon film (3) is deposited on the ferromagnetic metal thin film (2). Let it form. The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be determined experimentally. Further, by applying a voltage of 0 KV to -3 KV to the electrode arranged on the non-magnetic substrate (1) side, the hardness of the carbon film (3) can be increased, and the carbon film (3) and the ferromagnetic Adhesion with the metal thin film (2) can be improved. As hydrocarbon gas, methane, ethane,
Propane, butane, pentane, hexane, heptane, octane or benzene can be used.

In order to form a hard carbon film (3),
It is desirable to increase the discharge energy, and it is also desirable to keep the temperature of the non-magnetic substrate (1) high. For example, the discharge energy is desirably set to an effective value of 600 V or more by superimposing an alternating current, for example, a high-frequency current and a direct current.

In the present invention, a nitrogen-containing plasma polymerized film (not shown) is formed on the surface layer of the carbon film (3), and the lubricant layer (4) is formed on the nitrogen-containing plasma polymerized film of the carbon film. Is preferred. The formation of the nitrogen-containing plasma polymerized film results in the presence of amino groups in the surface layer of the carbon film. As a result, the adhesive strength between the lubricant layer and the carbon film is increased, and the magnetic recording medium The durability is further improved. And, combined with the inclusion of a specific fluorine-containing compound in the lubricant layer, the running durability and the weather storage stability have been improved with excellent lubrication performance without impairing the electromagnetic conversion characteristics. A magnetic recording medium is obtained.

The nitrogen-containing plasma polymerized film is obtained by gasifying and introducing an amine compound such as propylamine, butylamine, ethylenediamine, propylenediamine or tetramethylenediamine into a vacuum vessel, and increasing the pressure in the vessel to 1.33.
× 10 ^{-1 to} 1.33 × 10 ² Pa (0.001 to ¹ Torr)
In this state, a high-frequency discharge is generated inside the vacuum container to form the vacuum container. By forming the nitrogen-containing plasma polymerized film, the chemical adsorption power of the lubricant composition is improved, and as a result, the adhesion strength between the lubricant layer and the carbon film is improved. The film thickness of the nitrogen-containing plasma polymerized film is suitably less than 3 nm. If the nitrogen-containing plasma polymerized film is thicker than this, the protective effect of the carbon film is reduced. Methods for forming a nitrogen-containing plasma polymerized film on the surface of a carbon film are described in U.S. Pat. Nos. 5,540,957 and 5,637,3.
No. 93, the contents of which are hereby incorporated by reference into these patents, form a part of the present specification.

The lubricant composition constituting the lubricant layer (4) is as described above. In the present invention, the amount of the lubricant composition of the present invention contained in the lubricant layer (4) is preferably 0.5 to 30 mg, and preferably 1.5 to 15 mg per 1 m ² of the surface of the lubricant layer. More preferably, there is. In order for such a small amount of the compound to be uniformly present in the lubricant layer, the lubricant layer of the magnetic recording medium of the present invention is desirably formed by the following method.

The lubricant layer (4) is formed by forming a ferromagnetic metal thin film (2) and a carbon film (3) on one surface of the non-magnetic substrate (1) in this order by using a conventional material and means. It is formed on the carbon film (3). The step of forming the lubricant layer (4) includes:
A lubricant containing the lubricant composition of the present invention is dissolved in a mixed organic solvent of a hydrocarbon-based solvent and an alcohol-based solvent to prepare a coating solution, which is prepared in an environment where the relative humidity is in the range of 10 to 40%. And a step of coating on the carbon film (3).

The hydrocarbon solvents that can be used in the present invention include, for example, toluene, hexane, heptane, and octane. The alcohol solvents that can be used in the present invention include, for example, methyl alcohol, ethyl alcohol, propyl alcohol, and isopropyl alcohol. Is a lower alcohol. Specifically, the mixed organic solvent is preferably a mixed solvent of toluene and isopropyl alcohol, a mixed solvent of hexane and isopropyl alcohol, or a mixed solvent of heptane and isopropyl alcohol. If the proportion of the alcohol-based solvent is too large, coating unevenness tends to occur. On the other hand, if the proportion of the hydrocarbon-based solvent is too large, it is uneconomical, so that the mixing ratio of the two is 1: 9 to 9: 1 by weight.
, Preferably in the range of 3: 7 to 7: 3. The concentration and the coating thickness of the coating liquid are selected so that the thickness of the lubricant layer (4) formed on the carbon film (3) after the evaporation of the solvent becomes a desired thickness. Generally, the concentration of the lubricant composition is 100 ppm or more.
It is preferable to apply a coating solution of 4000 ppm to a thickness of 1 μm to 50 μm.

The coating solution is preferably applied in an environment where the relative humidity is in the range of 10 to 40%. When the relative humidity is less than 10%, there is a problem that static electricity is easily generated, and equipment for creating an environment of such humidity is expensive. When the relative humidity exceeds 40%, there is a problem that coating unevenness is likely to occur.

The optimum thickness of the lubricant layer (4) is determined according to the lubricant composition, and the thickness is generally 3 to 5 nm.
The coating method may be any of a bar coating method, a gravure coating method, a reverse roll coating method, a die coating method, a wet coating method such as a dip coating method or a spin coating method, or an organic vapor deposition method.

After the application of the coating solution, a drying treatment is performed to evaporate the organic solvent, whereby a layer (4) of the lubricant composition is formed on the carbon film (3). By heating the drying process,
Alternatively, it can be carried out by natural drying. Then, the thickness of the finally obtained lubricant layer is preferably about 3 to 5 nm. However, since there is an optimum range of the thickness of the lubricant layer depending on the composition of the lubricant, the thickness of the lubricant layer is not necessarily limited to this range.

As described above, by forming a lubricant layer at a predetermined relative humidity using a specific mixed organic solvent, a lubricant layer having a uniform thickness without coating unevenness can be obtained, and the solvent can be used as the final solvent. After evaporation, a very thin lubricant layer of several nm can be formed. As a result, a highly reliable magnetic recording medium having excellent lubrication performance can be obtained.

The back coat layer (5) is made of polyurethane,
The layer is formed of one or more materials selected from nitrocellulose, polyester, carbon, calcium carbonate, and the like, and preferably has a thickness of about 500 nm. The back coat layer is formed, for example, by a wet coating method in which a coating solution obtained by dissolving and dispersing the above material in an appropriate solvent (for example, a mixed solvent of toluene and methyl ethyl ketone) is applied to the reinforcing layer, and then dried and the solvent is evaporated. Can be formed.

[0058]

EXAMPLES Next, specific examples of the present invention will be described, but the present invention is not limited to these examples.

(Example 1) As the nonmagnetic substrate (1), protrusions having a width of 500 mm, a thickness of 4.6 μm, a height of 30 nm and a diameter of 200 nm were formed on the non-magnetic substrate (1) in a range of 10 ⁵ to 10 ⁵ per 1 mm ^2.
Nine polyethylene naphthalate films were used. The number of protrusions is a value measured by STM analysis. On the surface of the non-magnetic substrate (1), a 180 nm thick ferromagnetic metal thin film (Co (80) -Ni (20) (mixed atom% in parentheses) is formed by oblique vacuum evaporation while introducing oxygen. 2) was formed.

Next, a 30% solids solution of methyl ethyl ketone / toluene / cyclohexanone composed of polyurethane, nitrocellulose and carbon black is applied to the back surface of the non-magnetic substrate (1) by a reverse roll coater, and the thickness after drying is applied. A back coat layer (5) having a thickness of about 500 nm was formed.

Next, a plasma is formed on the ferromagnetic metal thin film (2).
A carbon film (3) having a thickness of 15 nm is formed by a CVD method.
Was. Hexane gas and argon gas in a vacuum vessel
And a gas mixed with a 4: 1 ratio (pressure ratio).
Total gas pressure 4.0 × 10 ¹Pa (0.3 Torr)
However, the frequency of 20KHz, the voltage of 1500V AC and 1
000V DC is superimposed and applied to the electrodes in the discharge tube
It formed by doing. In addition, the carbon film (3)
Introducing ropylamine gas, 6.67 Pa (0.05 Torr)
r) High-frequency plasma treatment at 10 KHz while maintaining the pressure
And a 2.5 nm thick nitrogen-containing layer is formed on the surface layer of the carbon film (3).
An oxygen plasma polymerized film was formed.

Next, a lubricant composition in which a compound represented by the following chemical formula (a1) and a compound represented by the following chemical formula (c1) were mixed at a molar ratio of 3: 7, was mixed with isopropyl alcohol and toluene. Is mixed in a weight ratio of 1: 1 to a mixed organic solvent having a concentration of 2000 ppm.
To prepare a coating solution. Then, this coating solution was applied to a thickness of 4 μm by a wet coating method using a reverse roll coater in an environment of 23 ° C. and 30% RH, and then dried. Finally, on the carbon film (3), 1
A 4 nm thick lubricant layer (4) containing 5 mg lubricant composition per m ² was formed.

The tape material prepared as described above was cut into a 6.35 mm width by a slitter to prepare a 6.35 mm width magnetic tape sample (total thickness 5.3 μm, 80 minutes length).

[0064]

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[0065]

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(Examples 2 to 11) In Examples 2 to 6, the compounds represented by the chemical formulas (a2) to (a6) were used. In Examples 7 to 11, the compounds represented by the chemical formulas (b1) to (b) were used.
Using the compound represented by 5), the respective compounds and the compound represented by the chemical formula (c1) have a molar ratio of 3: 7
The magnetic tape samples were produced in the same manner as in Example 1 except that the lubricant composition was used in such a manner as to satisfy the following ratio.

[0067]

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[0068]

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[0069]

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[0070]

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[0071]

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[0072]

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[0073]

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[0074]

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[0075]

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[0076]

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(Embodiments 12 to 22) Embodiments 12 to
17, the compounds represented by the chemical formulas (a1) to (a6) are used. In Examples 18 to 22, the compounds represented by the chemical formulas (b) are used.
1) to (b5) are used, and a lubricant composition is used in which each of the compounds and a compound represented by the following chemical formula (c2) are blended in a molar ratio of 3: 7. A magnetic tape sample was produced in the same manner as in Example 1 except that the magnetic tape samples were used.

[0078]

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(Example 23) Except for using a lubricant composition in which the compound represented by the chemical formula (a1) and the compound represented by the chemical formula (c1) were mixed at a molar ratio of 1: 9 Produced a magnetic tape sample in the same manner as in Example 1.

(Example 24) Except that a lubricant composition in which the compound represented by the chemical formula (a1) and the compound represented by the chemical formula (c1) were blended in a molar ratio of 5: 5 was used. Produced a magnetic tape sample in the same manner as in Example 1.

(Example 25) Except that a lubricant composition in which a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1) were blended in a molar ratio of 7: 3 was used. Produced a magnetic tape sample in the same manner as in Example 1.

(Example 26) Except that a lubricant composition in which the compound represented by the chemical formula (a1) and the compound represented by the chemical formula (c1) were blended in a molar ratio of 8: 2 was used. Produced a magnetic tape sample in the same manner as in Example 1.

(Example 27) Except for using a lubricant composition in which the compound represented by the chemical formula (b1) and the compound represented by the chemical formula (c1) were mixed at a molar ratio of 1: 9 Produced a magnetic tape sample in the same manner as in Example 1.

(Example 28) Except that a lubricant composition in which the compound represented by the chemical formula (b1) and the compound represented by the chemical formula (c1) were blended in a molar ratio of 5: 5 was used. Produced a magnetic tape sample in the same manner as in Example 1.

(Example 29) Except that a compound represented by the chemical formula (b1) and a compound represented by the chemical formula (c1) were used in a molar ratio of 7: 3 to be used as a lubricant composition Produced a magnetic tape sample in the same manner as in Example 1.

(Example 30) Except that a lubricant composition in which the compound represented by the chemical formula (b1) and the compound represented by the chemical formula (c1) were blended in a molar ratio of 8: 2 was used. Produced a magnetic tape sample in the same manner as in Example 1.

(Example 31) A magnetic tape sample was produced in the same manner as in Example 1, except that the step of forming a nitrogen-containing plasma polymerized film on the surface layer of the carbon film (3) was omitted.

Example 32 A magnetic layer was formed in the same manner as in Example 1 except that a mixed organic solvent in which isopropyl alcohol and toluene were mixed at a weight ratio of 8: 1 was used in the step of forming the lubricant layer. Tape samples were made.

(Example 33) In the same manner as in Example 1, except that a mixed organic solvent in which isopropyl alcohol and toluene were mixed at a weight ratio of 1: 8 was used in the lubricant layer forming step. Tape samples were made.

Comparative Example 1 The procedure of Example 1 was repeated, except that only the compound represented by the following chemical formula (x1) was used instead of the two-component lubricant composition used in Example 1.
A magnetic tape sample was produced in the same manner as in Example 1.

[0091]

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(Comparative Example 2) In place of the two-component lubricant composition used in Example 1, only a known lubricant represented by the following chemical formula (x2) was used.
A magnetic tape sample was produced in the same manner as in Example 1.

[0093]

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(Comparative Example 3) A method similar to that of Example 1 was used except that only the compound represented by the chemical formula (a1) was used instead of the two-component lubricant composition used in Example 1. Magnetic tape samples were prepared.

(Comparative Example 4) A method similar to that of Example 1 was used except that only the compound represented by the chemical formula (b1) was used instead of the two-component lubricant composition used in Example 1. Magnetic tape samples were prepared.

Comparative Example 5 A method similar to that of Example 1 was used except that only the compound represented by the chemical formula (c1) was used instead of the two-component lubricant composition used in Example 1. Magnetic tape samples were prepared.

Comparative Example 6 A magnetic tape sample was prepared in the same manner as in Example 1, except that only isopropyl alcohol was used in place of the mixed organic solvent consisting of isopropyl alcohol and toluene in the step of forming the lubricant layer. did.

Comparative Example 7 A magnetic tape sample was produced in the same manner as in Example 1 except that toluene was used instead of the mixed organic solvent consisting of isopropyl alcohol and toluene in the lubricant layer forming step. .

Comparative Example 8 A magnetic tape sample was prepared in the same manner as in Example 1 except that the coating solution was applied by a wet coating method using a reverse roll coater in an environment of 23 ° C. and 55% RH. Produced.

The following evaluation tests (1) and (2) were carried out on the 6.35 mm wide magnetic tape samples obtained in Examples 1 to 33 and Comparative Examples 1 to 8, respectively. Tables 1 to 4 show the results obtained in each test.

(1) Running durability test Commercially available digital VT modified for RF (high frequency) output measurement
R (Matsushita Electric Co., Ltd., NV-DJ1), each 6.3
The middle part of the 5 mm wide tape sample excluding the winding start and end points, and
The change in RF output after repeated reproduction for 1000 passes and 50 hours in an environment of 80 ° C. and 80% RH was measured. The results were expressed in decibels as the change after the test before the test.

The tape damage is caused by the post on the tape surface,
Running scratches caused by the fixed drum, sliding scratches caused by the magnetic head and the rotating drum, and the like were visually observed and observed with a differential interference microscope, and evaluated on a five-point scale. The evaluation criteria are as follows. 5: There is no problem in practical use. 4: There is no practical problem. 3: Practical, but needs improvement. 2: The tape is severely damaged and practically not practical. 1: The tape damage is too bad and there is no practicality at all.

The adhesion of the traveling system powder was evaluated on a five-point scale by visually observing the stains (the state of powder adhesion) on the post and the fixed drum after the tape was repeatedly reproduced for 1000 passes. The evaluation criteria are as follows. 5: There is no powder adhesion and there is no problem in practical use. 4: Slight powder adhesion is observed, but there is no practical problem. 3: Practical, but powdery and needs improvement. 2: Severe powder adhesion, practically no practicality. 1: Powder adhesion was too bad and practically not at all.

In order to measure the residual amount of the lubricant on the tape sample surface after the running durability test, fluorine atoms were analyzed by X-ray photoelectron spectroscopy (XPS) before and after the running durability test, and before and after the test. The remaining amount was calculated from the ratio of the intensities.

(2) Weathering Storage Test In order to evaluate the weathering storage of each 6.35 mm wide tape sample, the sample was left in an environment of 40 ° C. and 80% RH for 30 days to perform a weathering storage test. .

The still life after storage was measured using a commercially available digital VTR (Made by Matsushita Electric Co., Ltd., NV-
It was measured in an environment of 3 ° C. and 5% RH using DJ1). The still life after storage was shown as the time from the initial stage until a decrease of 6 dB.

Further, under an environment of 40 ° C. and 80% RH, 30
After standing for days, using a commercial digital VTR (Matsushita Electric Co., Ltd., NV-DJ1) modified for RF output measurement,
Reproduction was repeated for 100 passes and 133 hours in an environment of 23 ° C. and 60% RH, and head clogging was measured from the RF output during reproduction. During this repetitive playback, the RF output is 6d
It is assumed that head clogging has occurred when the pressure has decreased by B or more, and the time obtained by summing the times when such a decrease has been measured is regarded as head clogging.

[0108]

[Table 1] Running Durability Test Weathering Preservation Test Lowering Output Tape Running System Lubricant Remaining Still Head After Storage Example Example (dB) Name Powder Adhesion Amount (%) Life (min) Clogging (sec) 1 -1.0 5593>6002-1.255592>6003-1.44444915304-1.155593>6005-1.44487> 6006. -1.54489560.57-1.255592>6008-1.15559>6009-1.343491> 60010-1.44 488 55 0 11 -1.5 4 4 90 55 0.5

[0109]

[Table 2] Running durability test Weathering / storability test output decrease Tape running system Remaining lubricant still after storage Head Example Example (dB) Timer powder adhesion (%) Life (minutes) Clogging (seconds) 12-1.2 5591>60013-1.15593>60014-1.44492>60015-1.25593>60016-1.344486> 600 0.517-1.54489>60018-1.25593>60019-1.15592>60020-1.343491> 600.521- 1.4 4 487 570 22 -1.5 44 89 560

[0110]

[Table 3] Running durability test Weathering / storability test output decrease Tape running system Remaining lubricant Still storage After storage Example (dB) Name powder adhesion (%) Life (minutes) Clogging (seconds) 23 -1.0 5593>60024-1.155590>60025-1.244487570.526-1.544468520.527-1.15593>60028-1.055592> 600.529-1.344488550.530-1.544486560.531-1.54448281. 0 32 -1.44 485 560.5 33 -1.54 4486 550.5

[0111]

Table 4 Running Durability Test Weathering Preservability Test Output Decreasing Tape Running System Lubricant Remaining Still Head After Storage Comparative Example (dB) Tamper Powder Adhesion Amount (%) Life (min) Clogging (sec) 1-6.3 1 151 1 29.0 2 -6.6 1 153 1 27.0 3 -3.1 3 3 505 5 3.0 4 -2.6 3 3 7 18 19.5 5 -2.6 3 4 77 17 12.06 -3.0 3 486 27 27 4.0 7 -2.8 4 38 85 26 3.08 -3.1 33 88 24 4.0

As is clear from Tables 1 to 4, in comparison with Comparative Examples 1 to 8, all of the magnetic tapes obtained in Examples 1 to 33 show a small decrease in output even after repeated running. Even after repeated running, the residual amount of the lubricant is large (that is, the scattering of the used lubricant is small),
The tape had excellent characteristics such as no problem of tape damage, little adhesion of running system powder, little head clogging during repeated running after storage, and good still life after storage.

In particular, even when the number of repetitions of the reproduction was increased to 1000 passes in the running durability test, Examples 1-33 were performed.
The small tape damage in magnetic tape
This shows that the magnetic recording medium of the present invention has excellent running durability. Further, in Examples 1 to 33, the fact that the running system powder adheres little means that the magnetic tape of the present invention runs well on the tape running system, and the frictional force that causes the powder to separate from the magnetic recording medium during the running of the tape is magnetic. This shows that it hardly occurs between the recording medium and the tape running system. Therefore, when the magnetic recording medium of the present invention is used, it is possible to suppress the occurrence of a traveling trouble due to powder adhesion in the traveling system.

The magnetic tapes of Examples 1 to 30 were prepared by using Comparative Examples 1 and 2 using a conventional lubricant and a lubricant layer containing only the compound represented by the general formula (a1), (b1) or (c1). In all, as compared with Comparative Examples 3 to 5 in which was formed, excellent running durability and weather resistance storage stability were exhibited. Thus, on the carbon film (3), at least one compound selected from the compounds represented by the general formulas (a) and (b) and at least one compound selected from the compounds represented by the general formula (c) Each of the magnetic tape samples of Examples 1 to 30 in which the lubricant layer (4) was formed with the lubricant composition containing the compound of (1) above, was clearly excellent in practical reliability such as running durability and weather storage stability. ing.

The magnetic tape sample of Example 31 uses the same lubricant composition as in Example 1, but does not form a nitrogen-containing plasma polymerized film on the carbon film (3).
The running durability and weather resistance of Example 31 are slightly inferior to those of Example 1. This indicates that the nitrogen-containing plasma polymerized film contributes to the improvement of the lubrication performance of the magnetic tape.

From Example 1 and Comparative Examples 6 and 7, the coating liquid prepared by dissolving the lubricant composition of the lubricant layer (4) in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent was used as a carbon film. (3) It can be seen that a magnetic tape sample excellent in practical reliability, such as running durability and weather storage stability, can be stably manufactured by forming a lubricant layer (4) by coating on the lubricant tape. In Comparative Example 8 in which the coating liquid containing the lubricant composition was applied under high humidity, the running durability and the weather resistance storage stability were obtained even though the same lubricant composition as in Example 1 was used. Are inferior, indicating that application under high humidity is undesirable.

In Examples 1 to 33, the reverse roll coating method, which is a wet coating method, was employed in the step of forming the lubricant layer (4). ) Can be formed.

Although the embodiment in which the magnetic recording medium of the present invention and the method of manufacturing the same are applied to a commercially available digital VTR tape has been described above, the magnetic recording medium of the present invention and the method of manufacturing the same are not limited thereto. It can also be applied to other metal thin-film magnetic tapes, magnetic disks, etc., such as tapes for data storage.

[0119]

As described above, the lubricant composition of the present invention in which two or more specific fluorine-containing compounds are combined exhibits excellent lubrication performance. Then, by forming a lubricant layer of a magnetic recording medium with this lubricant composition, an adhesive strength of the lubricant layer to the carbon film is improved, and a magnetic recording medium of the present invention exhibiting good lubrication performance is obtained. Can be. Accordingly, the magnetic recording medium of the present invention using the lubricant of the present invention as a lubricant layer has improved running durability and weather resistance preservation without impairing the electromagnetic conversion characteristics due to a synergistic effect of these, and This is a practically reliable magnetic recording medium with very little scattering of lubricant during use.

Further, by forming a nitrogen-containing plasma polymerized film on the surface layer of the carbon film in the magnetic recording medium of the present invention, the chemical adsorption power of the lubricant composition is improved, so that the lubricant layer adheres to the carbon film. It is possible to obtain a magnetic recording medium with further improved strength and excellent lubrication performance. By these synergistic effects, the magnetic recording medium of the present invention has improved practical durability such as running durability and weather storage stability without impairing the electromagnetic conversion characteristics.

The magnetic recording medium of the present invention is manufactured by a manufacturing method including a step of applying a coating solution prepared by dissolving a lubricant layer composition in a specific solvent on a carbon film under a specific humidity condition. Is done. By using this coating liquid, a lubricant layer having a uniform thickness without coating unevenness can be obtained. Further, by limiting the range of the humidity, deterioration of the performance of the lubricant layer is prevented. Therefore, according to the production method of the present invention, it is possible to stably produce the magnetic recording medium of the present invention which is excellent in practical reliability such as running durability and weather storage stability.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a metal thin-film magnetic tape which is one embodiment of the magnetic recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic substrate 2 Ferromagnetic metal thin film 3 Carbon film 4 Lubricant layer 5 Back coat layer 10 Magnetic recording medium (magnetic tape)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C10N 30:00 C10N 30:00 EZ 40:18 40:18 (72) Inventor Tetsuo Fuchi Osaka Prefecture 1006 Kadoma Kadoma Matsushita Electric Industrial Co., Ltd. F-term (reference) 4H104 BD07A CD04A LA15 LA20 PA16 5D006 AA01 AA02 AA05 AA06 FA02 FA05 FA06 5D112 AA07 AA11 AA22 BC02 BC05 BC10

Claims (8)

[Claims] 1. I) at least one compound selected from compounds represented by the general formulas (a) and (b) having a perfluoroalkyl group or a perfluoropolyether group and an alkyl group or an alkenyl group in a molecule. And II) a lubricant composition comprising at least one compound selected from the compounds represented by the general formula (c): (Wherein, R ¹ represents an alkyl group or an alkenyl group;
R ² represents a perfluoroalkyl group or a perfluoropolyether group; a is an integer of 0 to 20;
Or 1) (Wherein, R ³ represents an alkyl group or an alkenyl group;
R ⁴ represents a perfluoroalkyl group or a perfluoropolyether group, R ⁵ represents —O— or —S—,
c is an integer of 0 to 20, and d is 0 or 1. (Wherein, R ⁶ represents a fluorine-containing organic group, R ⁷ represents an alkyl group or an alkenyl group, and n is an integer of 0 to 12). 2. The compound represented by the general formula (c), wherein R ⁶ is a fluoroalkyl group, a perfluoroalkyl group, a fluoroalkenyl group, a perfluoroalkenyl group, a fluoroether group, a perfluoroether group, or a fluoropolyether. The lubricant composition according to claim 1, which is a group or a perfluoropolyether group. 3. The compound represented by formula (a) or (b), wherein the perfluoropolyether group is represented by any of formulas (d), (e) and (f): The lubricant composition according to claim 1 or claim 2: (In the formula, q is an integer of 1 or more.) (In the formula, r and t are integers of 1 or more.) (Wherein, R ⁸ represents a perfluoroalkyl group, and u represents 1)
And v is an integer of 1 to 30). 4. The mixing ratio of at least one compound selected from the compounds represented by the general formulas (a) and (b) and at least one compound selected from the compounds represented by the general formula (c) is molar. The lubricant composition according to any one of claims 1 to 3, wherein the ratio is in the range of 1: 9 to 8: 2. 5. A magnetic recording medium comprising: a ferromagnetic metal thin film provided on one surface of a nonmagnetic substrate; and a lubricant layer provided on the ferromagnetic metal thin film via a carbon film. A magnetic recording medium, wherein the agent layer contains the lubricant composition according to any one of claims 1 to 4. 6. The magnetic material according to claim 5, wherein the carbon film has a nitrogen-containing plasma polymerized film on a surface portion thereof, and the lubricant layer is formed on the nitrogen-containing plasma polymerized film of the carbon film. recoding media. 7. The method for manufacturing a magnetic recording medium according to claim 5, wherein the step of forming the lubricant layer comprises adding a lubricant composition to the mixed organic solvent of a hydrocarbon solvent and an alcohol solvent. The coating solution prepared by dissolving
A method for producing a magnetic recording medium, comprising a step of applying the composition on a carbon film in an environment within a range of 0 to 40%. 8. The method according to claim 7, wherein the mixing ratio of the hydrocarbon solvent and the alcohol solvent is in the range of 1: 9 to 9: 1 by weight.